Support tasks injection into a running VM.

test/cctest/test-debug.cc

Index: test/cctest/test-debug.cc
diff --git a/test/cctest/test-debug.cc b/test/cctest/test-debug.cc
index c3c65fd2f0256113f9594b29681ce2e136e0a76a..84d45ff4de2963eede546cf5446fa4c476b0f9fe 100644
--- a/test/cctest/test-debug.cc
+++ b/test/cctest/test-debug.cc
@@ -7396,6 +7396,52 @@ TEST(DebuggerCreatesContextIffActive) {
 }
 
 
+class DelayedTask : public v8::base::Thread {
+ public:
+  DelayedTask(v8::Isolate* isolate, v8::Debug::Task* task, int delay_ms)
+      : Thread(Options("DelayedTask")),
+        isolate_(isolate),
+        task_(task),
+        delay_ms_(delay_ms) {}
+  void Run() override {
+    v8::base::OS::Sleep(delay_ms_);
+    v8::Debug::BreakAndRun(isolate_, task_);
+    task_ = NULL;
+  }
+
+ private:
+  v8::Isolate* isolate_;
+  v8::Debug::Task* task_;
+  int delay_ms_;
+};
+
+
+class StopExecutionTask : public v8::Debug::Task {
+ public:
+  explicit StopExecutionTask(LocalContext& context) : context_(context) {}
+  void Run() override {
+    context_->Global()->Set(v8_str("stop"), v8::True(context_->GetIsolate()));
+  }
+
+ private:
+  LocalContext& context_;
+};
+
+
+TEST(RunTaskWhileLooping) {
+  LocalContext env;
+  v8::HandleScope scope(env->GetIsolate());
+
+  v8::Debug::Task* task = new StopExecutionTask(env);
+  // Delaying the task increases probability the task is injected while the

[Benedikt Meurer, 2014/12/18 04:11:57]

This is rather fragile. Can we have a more robust test case?

[Sven Panne, 2014/12/18 08:27:51]

I would even go a step further: Without proper synchronization, this is not
LGTM. We don't want to have "CPUProfiler reloaded" with all those flakes on the
bots... ;-)

[alph, 2014/12/18 14:28:03]

This test case it robust. It does not fail/flake depending on the timeout value.
By adding the timeout I just wanted to increase the probability the task is
fired when VM is already running a pure-JS tight loop.

However, as Yury pointed out in an offline chat, the purpose of this test is not
to check the interrupts work for tight loops. But to check  that the task gets
executed.

So I remove the Sleep once you insist.

[alph, 2014/12/18 14:28:03]

Again, this Sleep does not lead to flakiness. There's no race. Instead it made a
better test coverage of time moments the task is injected.

Anyway I removed it, once it's so frightening.

+  // loop is already running.
+  DelayedTask delayed_task(env->GetIsolate(), task, 10);
+  CompileRun("var stop = false;");
+  delayed_task.Start();
+  CompileRun("while (!stop) {}");
+}
+
+
 TEST(LiveEditEnabled) {
   v8::internal::FLAG_allow_natives_syntax = true;
   LocalContext env;